1. Field of the Invention
The present invention relates to a latch device, and more particularly, to a latch device for releasing a half-closed state and a fully-closed state of a door body held by a latch mechanism.
2. Description of the Related Art
As a latch device provided on a vehicle such as a four-wheel automobile, a latch device having a latch mechanism and an open lever has been known. The latch mechanism includes a latch and a ratchet.
The latch is pivotally supported on a door body of, for example, a side door via a latch shaft, and is arranged so as to be oscillatable around the axis of the latch shaft in modes of opening operation and closing operation. The latch is always biased in the direction of opening operation by a latch spring, which is a biasing unit, and performs a closing operation against the urging force created by the latch spring as a result of the closing operation of the door body, thereby becoming a state of being engaged with, for example, a striker disposed on a vehicle body.
Similar to the latch, the ratchet is pivotally supported on a door body via a ratchet shaft, and is arranged so as to be oscillatable around the axis of the ratchet shaft in modes of engaging operation and disengaging operation. The ratchet is always biased in the direction of engaging operation by a ratchet spring, which is a biasing unit, and is engaged with the latch by the engaging operation performed by the urging force of the ratchet spring to maintain the state in which the latch is engaged with the striker, and on the other hand, releases the engaging state by performing the disengaging operation against the urging force of the ratchet spring.
The open lever connects with an operating handle provided on the door body, namely, an outside handle provided on the outside of the side door and an inside handle provided on the inside of the side door, and is arranged so as to be oscillatable in a mode of door opening operation by the opening operation of the operating handle. The open lever disengages the ratchet against the urging force of the ratchet spring by the door opening operation.
In such a latch device, the latch and the striker are made in an engaging state by the closing operation of the door body, and the ratchet is engaged to maintain the engaging state, by which the door body is made in a half-closed state or a fully-closed state with respect to the vehicle body, and on the other hand, the operating handle is operated to open the door and the open lever is operated to open the door to release the engaging state, by which the door body is allowed to open.
In the latch device, the engaged ratchet is engaged with the ratchet in the state of being engaged with the striker and the engaged state is maintained, by which the door body is made in a half-closed state or a fully-closed state with respect to the vehicle body. However, depending on the type of latch device, especially when the door body is in a fully-closed state with respect to the vehicle body, in a portion in which the ratchet engages with the latch, the reaction force (urging force) of the latch spring and the reaction force of a seal member, such as a weather strip, provided between the vehicle body and the door body acts, and resultantly a high frictional force may be generated.
Therefore, when the operating handle (the outside handle and the inside handle) is operated to open the door, and the open lever is operated to open the door to disengage the ratchet, the frictional force acts as a resistance force, by which the operation load of operating handle is increased than needed. Such an increase in operation load of the operating handle may cause a difficulty in opening operation of the operating handle for a user such as an old person, a child, a handicapped person, and a sick person.
To solve the problem, a latch device has been proposed that has a power release mechanism that disengages the ratchet by the power of a motor resulting from the opening operation of operating handle performed by the user to aid the opening operation of the operating handle (see, for example, Japanese Utility Model Application Laying-open No. H7-21956, Japanese Patent Application Laying-open No. 2003-278426, and Japanese Utility Model Application Laying-open No. H4-68182).
However, in the latch device proposed in the Patent Documents, a power mechanism having motor power, such as the power release mechanism, requires a high cost and an excessive installation space, which presents a problem in that the manufacturing cost is required, and the size of device increases.